For example, in electronic equipments such as a cellular phone, a group of circuit units for processing radio frequency signals having different frequencies, such as a microprocessor and a SWA filter, are mounted on the same circuit board. In such a case, there may be a problem in that an interference of radio frequencies occurs between the circuit units.
In order to solve such as problem, a shield member 5 (metal case) made of a metal is mounted on a circuit board 1 of a cellular phone to shield a group of electronic parts 2, as illustrated in FIG. 1. The shield member 5 is mounted on the circuit board 1, on which a solder paste is printed, simultaneously with mounting of the electronic parts 2 and electronic parts 3, and joined to the circuit board 1 by solder-reflow collectively. The problem of radio frequency interference may be solved by such a structure of having the shield member 5 made of a metal. However, on the other hand, there may occur another problem if a defect occurs in the electronic parts arranged inside the shield member 5.
When a defect occurs in one of the electronic parts 2, the defective electronic part 2 is removed from the circuit board 1, and a repair process is applied to replace the defective electronic part 2 with a good electronic part 2 (refer to Patent Document 1). Normally, the shield member 5 is mounted on the circuit board 1 to surround the electronic parts 2 arranged inside the shield member 5 with a small distance, such as about 1 mm, from the electronic parts 2.
Accordingly, if a replacement is needed for the electronic parts 2, there are many cases in which the shield member 5 prevents the replacement work from being carried out. Thus, in many cases, the electronic parts 2 must be replaced with other electronic parts 2 after removing the shield member from the circuit board 1. Because the shield member 5 is joined to the circuit board 1 in its entire circumference by soldering, the only one method to remove the shield member 5 is to melt the solder, which joins the shield member 5 to the circuit board 1.
In order to remove the shield member 5 from the circuit board 1, it is necessary to heat the entire solder-joined part of the shield member 5 simultaneously. Accordingly, using a method of heating a large area, such as using a hot air, was suggested. However, such a method was not actually used because it was difficult to acquire reliability of products after shipment due to a problem in that the electronic parts 2 arranged inside the shield member 5 and the electronic parts 3 arranged outside the shield member 5 are heated simultaneously to a temperature close to a melting point (217° C.) of the solder.
Thus, other methods to heat the shield member 5 alone were suggested, such as a method illustrated in FIG. 2A and a method illustrated in FIG. 2B. In the method illustrated in FIG. 2A, a heating head 100 is brought into contact with a top surface 5b of the shield member 5 to heat the solder 7 by a heat transmitted from an upper portion of the shield member 5. In the method illustrated in FIG. 2B, the heating head 100 is brought into contact with a side surface 5b of the shield member 5 to heat the solder 7 by a heat transmitted from a portion closer to the solder 7 than that of the method illustrated in FIG. 2A.    Patent Document 1: Japanese Laid-Open Patent Application No. 08-046351
However, because it is difficult to stably heat the solder 7 according to the above-mentioned methods illustrated in FIGS. 2A and 2B, those methods have not been used practically.
That is, according to the method illustrated in FIG. 2A, it is difficult to melt the solder 7 unless the temperature of the heating head 100 is raised to a temperature around 400° C. because the shield member 5 is normally made of a stainless steel plate with nickel or tin plating, which provides a poor heat conduction, and the heating position is distant from the solder 7. Additionally, if the heating head 100 having such a high-temperature is brought into contact with the shield member 5, color degradation progresses due to oxidation of the shield member 5, thereby raising a problem in that dusts are generated and an insulating layer is formed on a surface of the shield member 5, which degrades a shielding property of the shield member 5.
According to the method illustrated in FIG. 2B, in association with high-density mounting of the circuit board 1, there are many cases in which the electronic parts 3 are arranged at a small distance, such as 0.2 mm, from the position where the shield member 5 is arranged. Thus, it is very difficult to bring the heating head 100 into contact with the side surface 5a of the shield member 5.
If the solder 7 is melted by a contact-heating tool having a flat tip being brought into contact with the solder 7 instead of the heating head 100, a flux may adhere a surface of the contact-heating tool, which flux thermally insulates the contact-heating tool. Thus, it is difficult to melt the solder 7 surely. Additionally, it is necessary to clean the contact-heating tool after each operation in order to stably melt the solder 7, which raises a problem in that it is inconvenient for an operator to perform a cleaning operation.